High-density production of the rotifer <i>Brachionus plicatilis</i> in a recirculation system: consideration of water quality, zootechnical and nutritional aspects

Rotifers were reared on the artificial diet culture Selco® in batch and recirculation conditions at different water exchange rates. The different rearing conditions resulted in considerable changes in water quality, which in their turn affected rotifer growth and food consumption. At a daily water exchange rate of 100%, no positive effect was obtained in rotifer growth compared to the batch rearing system, but the rotifer culture period could be prolonged by 1 week. By increasing the daily water exchange rate from 100 to 300% the maximum rotifer density could be significantly (P -1. At the highest recirculation rate (daily water exchange of 500%) the highest rotifer production (2800 individuals per milliliter in 11 days) was obtained after adjustment of the feeding scheme. This adjustment was necessary to compensate for food losses in the recirculation system. The use of a modified culture Selco (CSH) could further improve the performance of the rotifers. Using this experimental diet, a rotifer density of 8000 individuals per milliliter could be obtained in 8 days without rinsing and restocking during the production period. When the rotifer populations were kept below their maximal density by daily harvests the culture period could be extended to more than 1 month. During this period the cultures were not subjected to any water exchange or restocking except the replacement of the water to compensate for the daily harvested rotifers (±20% of the standing population). In general terms it can be stated that the use of a recirculation system has proved to reduce labour and maintenance cost while ensuring stable physico-chemical rearing conditions resulting in more reliable and healthy rotifer cultures